diffusion
Diffusion is one of several transport phenomena in organisms. The phenomena that occurs is the movement of a substance in a liquid from high concentration to a lower concentration until the liquid is equally concentrated in every part. This occurs notably in the digestive tract as the things the body needs are taken from the stuff organisms eat and transported through diffusion in the small intestine (this is true for snakes to) to the blood stream to be transported by blood cells. The useful substances taken from the food the organism eat are diffused through villi (pictured above) in order to get to the blood stream. (2)
Sources
(1) http://en.wikipedia.org/wiki/Metabolism#Catabolism
(2) http://en.wikipedia.org/wiki/Diffusion
(2) http://en.wikipedia.org/wiki/Diffusion